magnetic fields

I don’t know what meal times are like in other homes, but in ours they tend to be chaotic and unpredictable. Take a simple breakfast last week as an example. Nothing too fancy… there was literally only cereal on offer. But cereal boxes can be great conversation openers, especially if they are from the BEAR company and are covered in all kinds of interesting facts.

“Are black holes real and what is spa-ghett-if-ication?” Asked the 11-year-old, cereal box in hand.

What is a Magnet?

A magnet is an object that can produce a magnetic force around it called a “magnetic field”. Magnets attract certain types of metals such as iron, nickel and cobalt.

Let’s learn more!

A magnetic field is not visible to the human eye, however iron filings can be used to show the pattern of a magnetic field. The magnetic field around all magnets is strongest at it‛s ends – these ends are called the Poles. One end is called the North Pole and the other is called the South Pole, just like the Earth.

If you put the poles of two magnets together they will either pull together (attract) or push apart (repel); Different poles attract (North and South), similar poles repel!

photo credit: daynoir via photopin cc

Did you know… small iron rocks on the Earth‛s surface are often natural magnets and these are called Lodestones.

The Earth as a magnet

The Earth is one big magnet – it‛s magnetic field is created by the iron that is in the core of the Earth. The Earth‛s magnetic field is strongest at the North Pole and the South Pole.

Did you know… the Earth‛s magnetic field deflects charged particles that come from the sun (Solar Wind) and this creates the wonderful lights called AURORA that can sometimes be seen in the sky.

Magnetic compasses use the Earth‛s magnetic field to determine North, South East and West.

Electromagnets

An electromagnet is a magnet that is produced when an electric current is passed around a piece of iron. Unlike true magnets, electromagnets are only magnetic while the electric current is switched on!

Did you know… the first person to notice that electric currents produce magnetism was a Danish scientist called Hans Christian Oersted, in 1820.

Some countries have started to use high speed trains called “MagLev” trains that are operated by powerful electromagnets.

These wheel less trains float on magnetic tracks and can reach speeds of more than 500 km/h.

Two experiments to try at home:

Make a compass:

You will need… a circle of paper, a needle, a magnet and a bowl of water.

What to do… thread the needle through the circle of paper so that nearly all the needle lies on one side of the paper (see below). Stroke the needle 30 times in one direction with one end of a strong magnet. Lift the magnet between strokes. Float the circle of paper on top of the water in the bowl (needle side up). The paper should spin around slowly for a few moments and then stop. The needle should now be pointing North-South. You can confirm this with a compass if you wish!

So what is happening? The needle contains little particles of iron that are all jumbled up. When the needle is stroked with the magnet it makes all the iron particles align in the same direction (North-South); the needle is temporarily magnetised!

What to do… wind the insulated wire tightly around the nail at least 30 times then ask an adult to strip back the insulation from both ends of the wire, exposing about 2 cm of the wire beneath. Using the blue tac stick one end of the wire to the + side of the battery and the other end to the – end. Now see if your electromagnet can pick up some paperclips. If you disconnect the batter the paperclips should fall!!

So what is happening? When the wire is attached to the battery it creates an electric current that runs through the wire, temporarily magnetising the iron particles in the nail. When the battery is disconnected the nail no longer acts as a magnet!

Hope you have fun with these this weekend! If you have a question or something to add please drop me a note in the comments below!